Device and method for measuring cavities and use of the device for determining roller alignments

ABSTRACT

A device for measuring cavities has a main body, at least one first distance sensor mounted on the main body and rotatable about an axis of rotation for contactlessly measuring distances in a radial direction with respect to the axis of rotation, a holder for fixing the device within the cavity in a position in which the main body assumes an orientation in which the axis of rotation of the first distance sensor coincides substantially with a center axis of the cavity, and at least one second distance sensor, arranged on the main body, for contactlessly measuring distances in a direction parallel to the axis of rotation, the axis of rotation passing through a detection area of the second distance sensor.

BACKGROUND OF THE INVENTION

The present invention relates to a device with a main body, at least onedistance sensor mounted on the main body and rotatable about an axis ofrotation for contactlessly measuring distances in a radial directionwith respect to the axis of rotation, while the axis of rotation of thedistance sensor coincides with a center axis of the cavity. Theinvention also relates to a method for measuring cavities by means ofsuch a device, in which the device is arranged within the cavity in aposition in which the main body assumes an orientation in which the axisof rotation of the distance sensor coincides with a center axis of thecavity, the distance sensor is rotated about the axis of rotation and atleast one distance from an inner wall of the cavity in a radialdirection with respect to the axis of rotation is contactlessly measuredwith the distance sensor. In addition, the present invention relates toa use of such a device for determining an alignment of at least onefirst roller, which is mounted rotatably about a first roller axis ofrotation, with respect to at least one second roller, which is mountedrotatably about a second roller axis of rotation parallel to the firstroller axis of rotation.

A self-propelled device for measuring cavities, and in particular formeasuring inside diameters of a shaft bore, is known for example from DE11 2006 003 388 B4. The device has a laser probe, which is arrangedrotatably about a center axis of the shaft bore on a measuring carriagethat can propel itself in the axial direction of the shaft bore. Thedistance by which the measuring carriage advances can be determined bymeans of a laser distance measuring instrument arranged outside theshaft bore.

By contrast, JP 2011-133385 A shows a device for measuring insidediameters with a first laser probe for measuring radial distances and asecond laser probe for measuring axial distances. In this case, thedevice is intended for being arranged off-center within a cavity to bemeasured.

SUMMARY OF THE INVENTION

The object of the present invention is to provide a versatile device anda method with which cavities can be measured particularly quickly andeasily, and also a further use for such a device.

This object is achieved by the device, the method, and by the use of thepresent invention. Preferred exemplary embodiments are discussed indetail herein.

According to the present invention, apart from the first distance sensorfor measuring radial distances, a second distance sensor for measuringdistances in a direction parallel to the axis of rotation, for example adistance from a reference point, reference object, reference body,reference place or a reference location, is additionally arranged on themain body, the axis of rotation passing through a detection area of thesecond distance sensor. Preferably, the detection area is flat and theaxis of rotation is oriented normal or perpendicular to the detectionarea. After fixing the device in the cavity, which is in particularcircular or is a cavity with a circular cross section, the axis ofrotation of the first distance sensor coincides substantially with thecenter axis of the cavity, so that consequently this center axis alsopasses through the detection area and the second distance sensormeasures distances in a direction parallel to the axis of rotation orcenter axis of the cavity or axial distances from the respectivereference object. In this case, the reference object may be locatedanywhere outside the cavity. For example, simply any wall may beintended as the reference object.

Since both the first distance sensor and the second distance sensor arearranged on the same main body, the device according to the invention ison the one hand compactly designed and can be handled very quickly,easily and conveniently in comparison with known devices, which eachrequire separate or external distance measuring devices that can bearranged and adjusted independently for measuring axial distances.Moreover, axial distances along the center axis of the cavity can bemeasured more accurately than is possible with separate or externaldistance measuring devices for measuring axial distances, since thesecond distance sensor does not first have to be laboriously, andtherefore unreliably, aligned or adjusted, whereby potential sources ofmeasuring errors are eliminated.

With the present invention, cavities can be measured for determiningtheir form, or deviations from a prescribed form, or for determining acenter or the middle of the cavity or a center or the middle of a crosssection of the cavity. In particular, cavities with large diameters, forwhich distances of over 500 mm can be measured, can be measured withgreat accuracy by the device according to the invention and the methodaccording to the invention.

The first distance sensor may be attached to the main body, which mayfor example be a housing, in such a way that, when the first distancesensor rotates, the main body together with the second distance sensor,likewise arranged on the main body, rotates about the same axis ofrotation. Also possible however are rotatable mountings of the firstdistance sensor on the main body, in the case of which the seconddistance sensor does not rotate together with the first distance sensorwhen it rotates but remains immovable. In this case, the rotation of thefirst distance sensor can be performed in a manual or automatic way.

For the evaluation of measured values that are generated, the device maybe provided with a corresponding processor. Furthermore, the device mayhave a memory for storing the measured values or an interface for thecable-bound or wireless transmission of the measured values to anotherdevice.

The first distance sensor is advantageously rotatable by a full circle,in order to be able to measure an inner wall of the cavity around thefull circumference. The first distance sensor is in this case preferablyrotatable by a full circle, the radius of which is also variablyadjustable. For this, there may be provided, for example, an arm that isadjustable or variable in length or can be extended and retracted, atthe end of which the first distance sensor is arranged. Depending on thetype of the first distance sensor and the distance from the inner wallof the cavity to be measured by it or the size of the cavity, in thecase of this embodiment the radius of the circle by which the firstdistance sensor rotates can be set by correspondingly adjusting thelength of the rotating arm.

In principle, any distance sensors or distance gauges for contactlesslymeasuring distances are suitable for the device according to theinvention. Thus, both distance sensors or distance gauges may becapacitive sensors, eddy-current sensors and sensors that are based onthe confocal triangulation principle. For reasons of simplicity,however, laser sensors with at least one laser source for emitting alaser beam and at least one detection area for detecting reflected laserbeams are preferred as the first distance sensor and/or the seconddistance sensor. In the case of the second distance sensor, thedetection area is the already mentioned detection area that is passedthrough by the axis of rotation. The detection area may be for examplethe area of a light-sensitive sensor, such as a photovoltaic cell, a PSDsensor or a CCD sensor. In this case, the laser sensors may operate forexample on the laser triangulation principle or on the transit-timeprinciple. The transit-time principle is suitable in particular in thecase of large diameters of over 1 m, as often occur in the case ofgenerators, since there the measured parts are often colored, and as aresult there are comparatively great tolerances.

Particularly preferably, both the first distance sensor and the seconddistance sensor is a laser sensor, the detection area of the seconddistance sensor being larger than that of the first distance sensor. Acomparatively large detection area of the second distance sensor isespecially advantageous whenever two or more cavities that aresubstantially in line, the center axes of which are however not exactlyin line or aligned with one another but are slightly displaced withrespect to one another, are measured by means of the same device. Evenin such cases, there is no disadvantageous impairment of themeasurement, since it is ensured by the large detection area of thesecond distance sensor that a laser beam emitted and reflected by thesecond distance sensor can impinge on the detection area of the seconddistance sensor.

In the case of a preferred embodiment of the device, the holder has anelongated form with two opposite ends, which are both intended to bearagainst an inner wall of the cavity. In other words, the holder extendstransversely through the cavity and bears with its opposite ends againstthe inner space at locations thereof lying diametrically opposite oneanother. Such a holder, which may be for example a spreading holder or aclamp, is distinguished by a lightweight and robust type ofconstruction. The holder may in this case be of any size and form,depending on the respective specific application, without any greatrequirements for accuracy.

A further preferred embodiment of the device according to the inventionhas at least one inclinometer and/or at least one gyroscope. By means ofan inclinometer, the inclination of the device, and consequently theinclination of the cavity in which the device is arranged, can bemeasured. By contrast, gyroscopes serve for determining the spatialposition. Information or data on the inclination or the spatial positionof cavities may be required for example for determining the spatialalignment of two or more cavities. Gyroscopes allow and simplify inparticular the measurement of vertically oriented cavities, the centeraxis of which is oriented perpendicularly or vertically.

In principle, the first distance sensor may be set up for performingdiscrete or point-by-point measurements of radial distances between thefirst distance sensor and an inner wall of the cavity, the firstdistance sensor being rotated by a certain angle after each measurement.On the other hand, the first distance sensor may also be set up forcontinuously performed measurements, which take place while the firstdistance sensor is rotating.

Particularly preferably, the measurement by means of the first distancesensor and the measurement by means of the second distance sensor takeplace simultaneously. Simultaneously performed measurements by means ofthe first distance sensor and the second distance sensor are inparticular preferred irrespective of whether discrete or continuousmeasurements are performed with the first distance sensor. As a resultof the simultaneity of the measurements, a time difference between themeasurements is eliminated, and values for the radial distance betweenthe first distance sensor and the inner wall of the cavity and for theaxial distance between the second distance sensor and the referenceobject are obtained for one and the same point in time, whereby themeasurements are more meaningful.

Furthermore, respective measurements with the first distance sensor areadvantageously carried out for at least two different distances of thesecond distance sensor from the reference point. By analogy with themeasurements with the first distance sensor, measurements with thesecond distance sensor can also be performed discretely or point bypoint. Thus, the distance of the second distance sensor from thereference object may be changed between each measurement, that is to sayfor example increased or reduced, or continuous distance measurementswith respect to the reference object may be performed with the seconddistance sensor, measurements which take place during a continuousadjustment of the distance between the second distance sensor and thereference object. In this way, it is possible for example to producespatial depth profiles of cavities.

The combination of the first distance sensor with the second distancesensor in the device according to the invention allows it to be used inparticular for determining the position of the center axis of the cavitywith reference to a prescribed axis or line. Particularly preferredtherefore is an embodiment of the method according to the invention inwhich a reference laser beam is provided along a line extending throughat least two cavities that are substantially in line with one another,the device is arranged successively in the two cavities in respectivepositions in which the reference laser beam falls onto the detectionarea of the second distance sensor, respective measurements are carriedout with the first distance sensor in both cavities and, on the basis ofthese measurements, respective distances of the axis of rotation fromthe reference laser beam are determined and, on the basis of thedistances determined, a relative position of the cavities in relation toone another or in relation to respective prescribed positions for thecavities is determined. Consequently, the alignment of cavities, such asfor example bores, can be determined in an easy way.

The combination of the first distance sensor with the second distancesensor additionally allows further uses of the device according to theinvention. Particularly preferred of these is a use for determining analignment of at least one first roller, which is mounted rotatably abouta first roller axis of rotation, with respect to at least one secondroller, which is mounted rotatably about a second roller axis ofrotation parallel to the first roller axis of rotation, the device beingarranged at a position in which the main body assumes an orientation inwhich the axis of rotation of the first distance sensor is parallel withreference to a plane formed by the first roller axis of rotation and thesecond roller axis of rotation, at least one distance from an end faceof the first roller being measured with the first distance sensor, thedevice being displaced along the axis of rotation and at least onedistance from an end face of the second roller being measured with thefirst distance sensor.

BRIEF DESCRIPTION OF THE DRAWING FIGURES

The invention is explained in more detail below on the basis ofpreferred embodiments and with the aid of drawings, in which:

FIG. 1 shows a device for measuring cavities arranged in a cavity;

FIG. 2 shows a side view of a device for measuring cavities;

FIG. 3a ) shows a cross section through two cavities, a device formeasuring cavities being arranged in a first of the cavities;

FIG. 3b ) shows the two cavities from FIG. 3a ), the device beingarranged in a second of the cavities; and

FIGS. 4a )-4 f) show a use of a device for measuring cavities fordetermining the alignment of a number of rollers.

DESCRIPTION OF THE INVENTION

In FIG. 1, an interior space or cavity 1 of a tubular body 2 with acircular cross section is represented. Arranged within the cavity 1 is adevice 3 for measuring cavities. The device 3 can also be seen in FIG.2, in side view without the body 2. Both FIGS. 1 and 2 are representedin a greatly simplified and schematic form for reasons of better overallclarity.

The device 3 also includes an elongated holder 4 with two ends 5 and 6that are remote from one another. The holder 4 extending transverselythrough the cavity 1, and aligned vertically in FIGS. 1 and 2, bearswith a first end 5 against an inner wall 7 of the cavity 1 at a lowerlocation in FIG. 1, while the holder 4 bears 1 with a second end 6 at anupper location of the inner wall 7, lying diametrically opposite thelower location of the inner wall 7. Here, the length of the holder 4 ischosen such that the device 3 is securely clamped in the body 2 and isfixed within the cavity 1.

The device 3 also has a pin 8, which is mounted on the holder 4 and isrotatable about an axis of rotation 9. Arranged on the pin 8 is acuboidal main body or housing 10, which moves with the pin 8 when itrotates. Between the holder 4 and the housing 10, a supporting bearing11 for the pin 8 is provided on a surface of the holder 4.

An extendable arm 12 with, arranged on it, a first laser sensor 13,which is intended for emitting a laser beam 14, is arranged laterally onthe housing 10. If the pin 8 or the housing 10 is rotated about the axisof rotation 9, the arm 12, and the first laser sensor 13 located at itsend, also describe a circle about the axis of rotation 9. In this case,the laser beam 14 is emitted by the first laser sensor 13 in a directionthat is perpendicular to the axis of rotation 9, and consequentlyradial. In FIGS. 1 and 2, the housing 10, the arm 12 and the first lasersensor 13 are represented in two different orientations. While in FIG. 1the first laser sensor 13 emits the laser beam 14 in a horizontaldirection to the left, the first laser sensor 13 can be seen after arotation by 90° in the direction of the arrow depicted in FIG. 1 andthen emits the laser beam 14 perpendicularly upwards. As is clear fromFIG. 1, the laser beam 14 impinges on the inner wall 7 and is reflectedback by it to the first laser sensor 13, where it is detected by adetector area of the first laser sensor 13 that is known per se and isnot represented any more specifically.

Finally, a side of the housing 10 that is facing away from the holder 4has a second laser sensor 15 and also an orientation means 16, whichcomprises a combination of an inclinometer and a gyroscope that is knownper se and therefore not set out any more specifically and serves fordetermining the spatial orientation of the device 3. By contrast, thesecond laser sensor 15 has a laser beam source or laser source 17 and adetection area 18. As FIG. 2 reveals, the detection area 18 is arrangedsuch that it is passed through by the axis of rotation 9. Furthermore,the detection area 18 is larger than the detection area (not shown) ofthe first laser sensor 13. The laser source 17 is intended for emittinga laser beam 19, which after reflection at a remote object, in the caseof FIG. 2 a wall 20 or some other stable reference surface, is returnedto the second laser sensor 15, impinges on the detection area 18 and isdetected by it. Ideally, the laser beams 14 and 19 are orientedperpendicularly in relation to one another or they form an angle ofsubstantially 90°.

Advantageously, the distance between the laser source 17 and the wall 20is comparatively great and in practice is 1 m or more. Particularlysuitable for this is a distance measurement on the basis of thetransit-time method. Instead of laser sensors 13 and 15, which are basedon the transit-time principle, in other embodiments it is however alsopossible for capacitive sensors, eddy-current sensors and sensors thatare based on the confocal triangulation principle to be used.

For measuring the cavity 1, the device 3 is first arranged within thecavity 1 and fixed there, as represented in FIG. 1. In this case, thehousing 10 assumes an orientation in which the axis of rotation 9coincides substantially with a center axis of the cavity 1 for allrotating angles, to be precise independently of the angle of rotation bywhich the housing 10, and with it the first laser sensor 13, arerotated. Then, the housing 10 or the first laser sensor 13 is manuallyor automatically rotated about the axis of rotation 9, whereby thecontinuously emitted laser beam 14 runs along the inner wall 7 of thecavity 1, is reflected back by it to the first laser sensor 15 and iscontinuously detected by the first laser sensor 13 or by its detectionarea. Using for example the known transit-time method, the radialdistance between the first laser sensor 14 and the inner wall 7 can bedetermined from the detected laser beam. In this way, the distancebetween the first laser sensor 13 and the inner wall 7 in a radialdirection is measured continuously for a full rotation of the housing10.

Simultaneously with the measurement of the radial distance, ameasurement of the distance or the axial distance between the secondlaser sensor 15 and the wall 20 is performed in an analogous way, thelaser beam 19 that is emitted by the second laser sensor 15 andreflected by the wall 20 being detected by the detection area 18 and thetransit-time method being applied.

Since the device 9 can be easily positioned and measurements of theradial and axial distance can take place at the same time as one anotheror simultaneously, it is possible to carry out the measurement of thecavity 1 in a comparatively short time. Moreover, the actual process ofperforming or carrying out of the measurements, in particular forproducing depth profiles of cavities 1, is found to be convenient,without additional measuring devices having to be provided outside thecavity 1 and laboriously adjusted. Because furthermore both themeasurement of radial distances and the measurement of axial distancesare carried out with the same device, the correlation between themeasured values obtained is improved, which ultimately leads to a moreexact and more reliable overall result.

The described device 3 is suitable in particular for measuring largecavities with diameters of over 400 mm and up to 3800 mm. The device 3can however also be used for diameters up to 8 m, such as those whichvertical hydro turbine generators have for example. Among the factorscontributing to this is that the detection area 18 of the second lasersensor 15 is larger than the detection area (not shown) of the firstlaser sensor 13. Furthermore, depending on how great the diameter of thecavity to be measured is, the length of the extendable arm 12 can beadjusted correspondingly. Moreover, the overall weight of the device 3is significantly reduced as a result of the simple design of the holder4.

Apart from just measuring cavities 2, because of its large detectionarea 18, the device 3 is for example also suitable in particular foraligning cavities that are in line with one another, such as for examplethrough-bores. In this respect, a first body 21 with a firstthrough-bore 22 is shown in FIG. 3a ). A second body 23 with a secondthrough-bore 24 is arranged alongside the first body 21, the firstthrough-bore 22 and the second through-bore 24 having substantially thesame dimensions. As can be seen in FIG. 3a ), although the firstthrough-bore 22 and the second through-bore 24 are in line with oneanother, the first through-bore 22 and the second through-bore 24 arenot aligned exactly in relation to one another, so that their centeraxes do not coincide exactly.

So, to determine the extent of the offset between the first through-bore22 and the second through-bore 24, the device 3 is first arranged in oneof the two through-bores 22 and 24. Without restricting the generality,FIG. 3a ) shows the device 3 arranged in the first through-bore 22.

Then a reference laser beam 25 is radiated from an external laser source(not shown) along a line extending through the two through-bores 22 and24. This line is generally the line on which the center axes of thethrough-bores 22 and 24 should lie when the through-bores 22 and 24 arealigned and their center axes are in line with one another. Since thesecond laser sensor 15 has a large detection area 18, the referencelaser beam 25 impinges on the detection area 18 even when the centerline of the first through-bore 22 that coincides with the axis ofrotation 9 is offset with respect to this line, as in FIG. 3a ).

The first through-bore 22 is measured in the way described above withthe first laser sensor 13 and the second laser sensor 15. On the basisof this measurement, both the position or the offset of the axis ofrotation 9, and consequently of the center axis of the firstthrough-bore 22, in relation to the reference laser beam 25 and thedistance of the first through-bore 22 or the first body 21 from areference point or reference object, for example from the laser sourcegenerating the reference laser beam 25, can be determined.

Subsequently, the device 3 is arranged in the second through-bore 24, ascan be seen in FIG. 3b ). Here, too, the size of the detection area 18is found to be advantageous, because it ensures impingement of thereference laser beam 25 on the detection area 18. The secondthrough-bore 24 is then measured in the same way as the firstthrough-bore 22, and both an offset of the axis of rotation 9 withreference to the reference laser beam 25 and the distance of the secondthrough-bore 24 or of the second body 23 from the reference object isdetermined.

The deviations of the two through-bores 22 and 24 from the desiredposition are then known and the positions of the bodies 21 and 23 can beadjusted correspondingly, in order to align the through-bores 22 and 24exactly with one another.

FIGS. 4a )-4 f) show a further possibility for using the device 3, inwhich the device 3 is used for determining alignments of rotatablerollers or rolls, as are used for example in printing machines, but alsoof complete blocks or frames on which such rollers or rolls may bemounted.

In FIG. 4a ), five rotatable rollers 26, 27, 28, 29 and 30 can be seen,the respective roller axes of rotation of which, which correspond torespective longitudinal axes of the rollers 26, 27, 28, 29 and 30, areparallel to one another. However, the rollers 26, 27, 28, 29 and 30,which are of the same length, are arranged offset with respect oneanother along their longitudinal axes. To be able to compensate for therespective offset of one of the rollers 26, 27, 28, 29 and 30, themagnitude of this offset with reference to a reference place must beknown.

Although in the present example of FIG. 4a ) the rollers 26, 27, 28, 29and 30 are of the same length, this does not necessarily have to be thecase. Rather, the alignment in relation to another of the rollers ofdifferent lengths can also be determined. For example, rollers ofdifferent lengths can be centrally aligned by determining a respectiveoffset of respective center lines of the rollers orientedperpendicularly to the respective longitudinal axes with respect to aprescribed reference line in a way corresponding to the method describedbelow.

For determining the offset, a reference laser beam 25 is emitted, asshown in FIG. 4a ), from a laser source (not shown), extending in FIGS.4a )-f) under end faces of the rollers 26, 27, 28, 29 and 30 andextending in or at least parallel to a plane formed by the roller axesof rotation. Then, the device 3 is arranged in such a way that thereference laser beam 25 impinges on the detection area 18 and the laserbeam 14 emitted by the first laser sensor 13 impinges as far as possiblein the peripheral region of an end face of the roller 26. In the case ofthis arrangement of the device 3, the axis of rotation 9 also extends inor at least parallel to the plane formed by the roller axes of rotation.Once the distance from the end face of the roller 26 has been measuredwith the first laser sensor 13, the device 3 is moved along thereference laser beam 25, so that the laser beam 14 emitted by the firstlaser sensor 13 then impinges at an opposite location of the peripheralregion of the end face of the roller 26, as shown in FIG. 4b ). In thisposition of the device 3, the measurement of the radial distance iscarried out once again. The distances of the end face of the roller 26obtained by the two measurements can be used to determine not only thedistance of the roller from the reference laser beam 25 but also itsinclination in relation to a line perpendicular to the reference laserbeam 25.

The described procedure is repeated for the other rollers 27, 28, 29 and30, which is shown in FIGS. 4c ) and 4 d) by way of example for theroller 27 and in FIGS. 4e ) and 4 f) for the roller 28.

By means of the data thus obtained, the positions of the rollers 26, 27,28, 29 and 30 can then be corrected and the rollers 26, 27, 28, 29 and30 can be aligned exactly in relation to one another.

It would be appreciated by those skilled in the art that various changesand modifications can be made to the illustrated embodiments withoutdeparting from the spirit of the present invention. All suchmodifications and changes are intended to be covered by the appendedclaims.

What is claimed is:
 1. A device for measuring cavities, comprising: amain body; at least one first distance sensor mounted on the main bodyand rotatable about an axis of rotation for contactlessly measuringdistances in a radial direction with respect to the axis of rotation; aholder for fixing the device within the cavity in a position in whichthe main body has an orientation in which the axis of rotation of thefirst distance sensor coincides substantially with a center axis of thecavity; and at least one second distance sensor, arranged on the mainbody, configured to contactlessly measure distances in a directionparallel to the axis of rotation, the axis of rotation passing through adetection area of the second distance sensor, wherein the device isconfigured and arranged for determining an alignment of at least onefirst roller, which is mounted rotatably about a first roller axis ofrotation, with respect to at least one second roller, which is mountedrotatably about a second roller axis of rotation parallel to the firstroller axis of rotation; the device being configured and arranged at aposition in which the main body assumes an orientation in which the axisof rotation of the first distance sensor is parallel with reference to aplane formed by the first roller axis of rotation and the second rolleraxis of rotation; the first distance sensor being configured andarranged to measure at least one distance from an end face of the firstroller; the device being displaced along the axis of rotation; and thefirst distance sensor being configured and arranged to measure at leastone distance from an end face of the second roller.
 2. The deviceaccording to claim 1, wherein the first distance sensor is rotatable bya full circle, the radius of which is variably adjustable.
 3. The deviceaccording to claim 1, wherein the first distance sensor and/or thesecond distance sensor is a laser sensor with at least one laser sourcefor emitting a laser beam and at least one detection area for detectingreflected laser beams.
 4. The device according to claim 3, wherein boththe first distance sensor and the second distance sensor is a lasersensor and the detection area of the second distance sensor is largerthan that of the first distance sensor.
 5. The device according to claim1, wherein the holder is elongated with two opposite ends, both of whichare bear against an inner wall of the cavity.
 6. A device for measuringcavities, comprising: a main body; at least one first distance sensormounted on the main body and rotatable about an axis of rotation forcontactlessly measuring distances in a radial direction with respect tothe axis of rotation; a holder for fixing the device within the cavityin a position in which the main body has an orientation in which theaxis of rotation of the first distance sensor coincides substantiallywith a center axis of the cavity; and at least one second distancesensor, arranged on the main body, configured to contactlessly measuredistances in a direction parallel to the axis of rotation, the axis ofrotation passing through a detection area of the second distance sensor,wherein the device is configured and arranged within the cavity andfixed by the holder in a position where the main body is oriented withthe axis of rotation of the first distance sensor coincidingsubstantially with a center axis of the cavity; the first distancesensor is configured and arranged to be rotated about the axis ofrotation and at least one distance from an inner wall of the cavity in aradial direction with respect to the axis of rotation is configured andarranged to be contactlessly measured with the first distance sensor;and the second distance sensor is configured and arranged to measure adistance in a direction parallel to the axis of rotation, wherein areference laser beam is provided along a line extending through at leasttwo cavities that are substantially in line with one another; the deviceis configured and arranged successively in the two cavities inrespective positions in which the reference laser beam falls onto thedetection area of the second distance sensor; whereby respectivemeasurements are carried out with the first distance sensor in bothcavities and, on the basis of these measurements, respective distancesof the axis of rotation from the reference laser beam are determinedand, on the basis of the distances determined, a relative position ofthe cavities in relation to one another or in relation to respectiveprescribed positions for the cavities is determined.
 7. The deviceaccording to claim 6, wherein the first distance sensor is rotatable bya full circle, the radius of which is variably adjustable.
 8. The deviceaccording to claim 6, wherein the first distance sensor and/or thesecond distance sensor is a laser sensor with at least one laser sourcefor emitting a laser beam and at least one detection area for detectingreflected laser beams.
 9. The device according to claim 8, wherein boththe first distance sensor and the second distance sensor is a lasersensor and the detection area of the second distance sensor is largerthan that of the first distance sensor.
 10. The device according toclaim 6, wherein the holder is elongated with two opposite ends, both ofwhich are bear against an inner wall of the cavity.
 11. The deviceaccording to claim 6, further comprising: at least one inclinometerand/or at least one gyroscope.
 12. The device according to claim 6,wherein the measurement by the first distance sensor and the measurementby the second distance sensor are configured to take placesimultaneously.
 13. The device according to claim 6, wherein respectivemeasurements with the first distance sensor are configured to be carriedout for at least two different distances of the second distance sensorfrom a reference point.